1. Technical Field
The present disclosure relates to resistance determining systems and, particularly, to a resistance determining circuit for determining resistances in an over voltage protection (OVP) circuit.
2. Description of Related Art
Power supply circuits usually include a protection circuit such as an OVP circuit. The OVP circuit will turn off the power supply circuit when an input voltage exceeds a predetermined voltage and will turn on the power supply circuit when the input voltage falls under another predetermined voltage. To respond to the change of the input voltage at the predetermined voltage, the OVP circuit often includes reference resistors which are used in defining and establishing the existence of the predetermined voltages.
Thus, the resistances of the references resistors need to be determined in designing the OVP circuit for a specific power supply circuit. At present, resistors of different resistances are placed into the OVP circuit under design on a trial-and-error basis, to function one by one as the reference resistor, until the OVP circuit under design can accurately respond to the significant change of the input voltage. This trial-and-error method is very inefficient.
Therefore, it is desirable to provide a resistance determining system for an OVP circuit which can overcome the limitations described above.